Crane drive system



Sept. 5, 1944. H. s. JACOBS ET AL CRANE DRIVE SYSTEM Filed Oct. 25,1941 4 sheets-sheet l |NVENTORS ATTORNEY Sept. 5, 1944. H. s. JACOBS ET AL CRANE DRIVE SYSTEM Filed Oct. 25, 1941 4 Sheets-Sheet 2 INVENTORS f ca/a @3f/MM BY ATTORNEY 4 Sheets-Sheet H. S. JACOBS ET AL.

CRANE DRIVE SYSTEM Filed OC.. 25, 19ML Sept. 5, 1944.

Sept. 5, 1944. Hs. JACOBS ET AL CRANE DRIVE SYSTEM Filed Ooi. 25, 1941 4 Sheets-Sheet 4 S R O T N E V N combustion engines, are in wide use.

' ment.

Patented Sept. 5, 1944 UNITED STATES PATENT oFFlcE CRANE DRIVE SYSTEM Henry S. Jacobs, Milwaukee, and Will S. Burdick, West Allis, Wis., assignors to Estnisch-feier Corporation, Milwaukee, Wis., a corporation of Wisconsin Application october 25, 1941, serial No. 416,596

' 5 Claims.

cluding afcontrollable torque transmitter which is dependent for its torque transmitting properties upon the reaction forces of eddy currents induced by controllable magnetic flux concentrations which are forced by the prime mover to traverse a conducting body.

Cranes and excavating cranes employingcontinuously running prime movers, such as internal Because of the power characteristics of such prime movers, the several instrumentalities to be driven in such cranes are customarily accelerated and driven by friction clutches. This permits the prime mover to continue running at fairly constant rate and at a rate at which power output and torque are fairly high. The speed of the prime mover in such cases is regulatedby a governor.

While friction clutches are suiiiciently effective for the above purposes to give to such machinery a high degree of utility, several distinctly disadvantageous properties are inherent in the friction clutch. One disadvantage is the continual wear of the friction linings. This necessitates frequent adjustment and periodic replacement of the friction bands or shoes. Another disadvantage is the considerable amount of effort required to actuate such clutches. y To overcome the latter difficulty, self-energizing clutches or servo actuators have been employed, but this gives rise to grabbing, touchiness in response, and a necessity for -even more frequent adjust- Another disadvantage of such friction clutches is that the speed at which they operate must be limited to avoid the effects of centrifugal force, which would interfere with proper functioning of the parts. In order to obtain sufilcient capacity at such lower speeds, such clutches must be made very large and heavy.

Even in the cas of friction clutches of goodA vrise to a peak with great suddenness. particularly true of the swing clutches, which are Even when disastrous grabbing is avoided and normal slipping engagement is preserved, the forces frictionally transmitted by friction clutches This is depended upon notv only to accelerate all of the swinging parts of the crane. but also to decelerate them and to reverse their direction of rotation. In other Words, said clutches are normally used to a considerable extent as brakes under conditions where the rate of slip amounts to 200% of full driving speed. The peak torque demand placed upon the prime mover by this arrangement is sufllciently severe to markedly slow down the running speed of the prime mover and to do so in a very short time interval. The action is so fast that the prime mover governor cannot respond in time to offset the deceleration. The characteristics of the internal combustion engine are such that power output ability falls off with loss of speed. By the time the governor comes into play the prime mover is no longer in condition to meet the load imposed. The power output of the engine is so impaired by the action that the swinging functions of the crane are rendered sluggish. This impairment of the power source also adversely affects the rate at which hoisting or other functions can be carried on simultaneously with swinging. While this aciverse property of the arrangement may be alleviated in part by skillful manipulation on the part ofthe operator, it cannot be eliminated.

Among the objects of this invention are: the elimination of frictionally engaging parts, with consequent avoidance of the frequent adjustment and replacement of friction members; the reduction of operator effort to the mere throwing of a switch; the elimination of all possibility of grabbing, with consequent elimination of the hazard attendant thereon; the limitation of peak torque demands so as to provide sufficient time for the prime mover governor to effectively meet K altering conditions and thus to increase the overal1 work capacity of the crane and the elimination of racking shocks and forces which produce unduly rapid deterioration of the machine. 'I'hese and other objects of this invention and the means by which the same are accomplished will become apparent from the description of the invention which follows. This invention is herein described by reference to the accompanying drawings which form a part hereof and in which there is set forth by way of illustration and not of limitation one i'orm of the apparatus of this invention.

In the dras: v

Fig. 1 is a side elevation, with parts broken away, ofa crane embodying one i'orm of the apparatus of this invention;

Fig. 2 is a plan view of the apparatus shown in Fig. 1;

Fig. 3 is a fragmentary detailed end elevation, partly in section, of the eddy current coupling means viewed as indicated by the broken lines 3 3 in Figs. 2 and 4;

Fig. 4 is a detailed side elevation, with parts broken away, of the eddy current coupling means; and

Fig. 5 is a wiring diagram of the electrical circuit employed in the apparatus of this invention.

Referring now to the drawings, there is shown in Fig. 1 a cab I mounted for' rotation upon a vcrawler base 2. A fragment of a boom 3 is shown mounted in conventional manner on the forward end of the cab, A prime mover in the form of an internal combustion engine 4 is located at the rear of the cab l, as shown. The prime mover 4 is of the continuously running type, regulated by a governor 5 which controls the throttle 6. Power from the prime mover 4 is delivered through gearing 1, 8, and 9 to the jack-shaft i0. The jack shaft I0 serves to deliver through continuously running gear il and l2 power for the operation of drum-shaft i3. Jack-shaft lo also extends across the cab l through the magnetic coupling means i4 and i5, which serve to deliver power for causing swinging motion of the crane.

In the form of the apparatus shown and herein described, the instrumentalities mounted upon the drum-shaft i3 for performing the various hoisting functions of the crane are arranged to be frictionally driven in the conventional manner and the details thereof are therefore not described. Themagnetic coupling means i4 and i5, however, employed to regulate the swingingmotion of the crane, are of novel form not heretofore employed in the driving system of cranes.

Magnetic coupling means i5 comprises a driv-` ing portion I8 which is keyed to thejack-shaft I0 to turn therewith. The driving member I6 is in the form of a wheel having a massive rim Il carried on a plurality of spokes It which are integrally formed with the hub i9. The massive rim Il is provided with a peripheral groove 20 in which there is accommodated a pair of peripheral magnetic windings 2|. The outer periphery of the rim l1 is slotted transversely by alternate deep and shallow ,slots 22 and 23 forming a plurality of outwardly extending pole pieces 24 which extend outwardly along the sides of the coils 2l, the pole pieces 24 being forked at their outer ends by reason of the slots 23 positioned therein. Opposite each of the polo pieces 24, standing to the. left in Fig. 3, are located integrally-formed radial ns 25, which extend inwardly toward the hub i9, 'as shown. The ns 2B serve to enhance the rate of ow of air through the apparatus.

Also radially held with respect to the ,lackshaft I0 to turn therewith is the insulating disk 28. The disk 26 is held securely in place between the sleeves 2l and 28, as shown. Mounted upon the opposite sides of the insulating disk 26 are slip-rings 29 and Bil, the same being held in place by through-bolts 33. An insulated bushing 34 serves 'to insulate the through-bolt 33 which passes therethrough from the slip-ring and, in like manner, the insulating bushing 35 serves to insulate the through-bolt which passes therethrough from the slip-ring 29.

Theinner ends of the coils 2| are brought convenient.

through leads and terminals into electrical connection with slip-ring 29, while the cuter ends of the coils 2i are brought by leads and terminals Si into electrical connection with slip-ring 3G. The two parts of the pair of coils 2i are thus placed in shunt connection with one another. It is obvious that the windings may consist of a single coil or several coils, as may bedesired or In the present instance two coils have been shown to permit reconnection for two different exciter' voltage ranges, purely as a matter of convenience.

Secured to the left-hand face of the rim il, as viewed in Fig. 3, by means ofthe bolts 38, is a side nger plate 39. The periphery of the side finger plate 39 is slotted by alternate deep and shallow slots 40 and 4I, respectively, to form the forked pole fingers 42, as shown.

Mounted to turn upon the jack-shaft i is a driven coupling member 43, which is held in place for free turning movement upon the roller-bearing 44. The bearing 44 is of the conical thrust type so that the driven member 43 is held positively against endwise displacement with respect to the shaft i.` The driven member 43 comprises the mounting disk 45 to which the cylindrical sleeve 46 is secured by bolts 41, as shown. The internal diameter of the cylindrical sleeve 4S is very slightly larger than the diameter of the path swept by the outer tips of the pole pieces 24 so that avery small air-gap extends between the sleeve 46 and the ends of the pole pieces 24.

, In the drawings this air-gap is shown slightly exaggerated for the purpose of clarity. The

Y sake of clarity.

Keyed to the mounting plate 45 of the driven member 43 is the bevel-pinion 48, which is contained within the reverse gear casing 49. The pinion 48 is positioned to mesh with a driven bevel-pinion 55 secured to the end of vertical shaft 5l, which extends downwardly, as shown,

from the gear casing 49.

The magnetic coupling means I4 mounted up= on the opposite end of jack-shaft Iii is symmetrically similar in all respects to the. magnetic coupling means i5, the same being provided with a driving member 52 and s. driven member 53, which is rigidly associated with bevel-pinion 54.

In order to supply current to the windings 2i, slip ring brushes are positioned. to engage the slip-rings 29 and 30. One of these is shown in dotted form and designated by the numeral 55 in Fig. 4. When the windings 2i are excited by current supplied thereto through the slip-rings and brushes, as described, a strong magnetic field is established, following the course of the broken line 56. The flux of vthis field bridges the gap between the ends of slotted pole pieces 24 'and th cylindrical sleeve 45 extending through the cylindrical sleeve, as shown, When the driving portion I6 is rotated and the cylindrical sleeve 44 is stationary or lags behind the rate of rotation. of driving member i8, strong eddy currents are created in the ,sleeve 46.` According to wellknown principles, these eddy currents are of such course and direction as to react against the movement of the localized linx zones through the material of the sleeve 46. As a result, torque is transmitted from the driving member IB to the driven member 43, this torque being a function of the intensity of flux and the rate of slip between the driving and driven member. The power disappearance represented by the torque and rate of slip appears largely in the form of resist- `ance heat within the conducting sleeve 46. The

heat thus created causes the temperature of sleeve 46 to rise until the rate of heat dissipation therefrom equals the rate at which such heat is being generated. The draft of air caused by the configuration of the driving member i6 andthe fins 25 facilitates this heat dissipation and serves to keep the temperature of the cylindrical sleeve 46 within safe operating limits.

The rise in temperature occurring in the sleeve 46 causes the same to expand slightly, thus increasing the air gap between it and the pole pieces 24. This same expansion, however, tends to reduce the air gap between the sleeve 46 and the side ngers 42. A iiux path thus becomes established, as indicated by the broken line 51, which flux path has a reluctance not greatly differing from that of path 56. In this way thermal expansion effects are compensated for in such a way that operating characteristics remain substantially constant regardless of operating temperatures.

As appears more clearly in Fig. 1, the vertical shaft carries a pinion 58 which is in mesh with idler gear 59. The gear 59 meshes with gear 60, mounted to be connected by dog-clutch 6| with a swing pinion shaft 62. Mounted upon the lower end of the shaft 62 is a swing pinion 63 which meshes with internal ring gear 64, which is securely held upon the crawler base 2. The ring gear 64 is surrounded by a roller track 65 also secured to the crawler base 2 and interposed between the track 65 and the cab is a race of rollers 66. A central guiding gudgeon, concentric with the roller track 5, is employed in conventional manner, but not shown, and in this way the cab is mounted for swinging movement upon the crawler base 2. Swinging movement is brought about by driving the pinion63, which is accomplished when desired by engaging the dog-clutch 6| and by energizing the windings of drive members |6 or 52.

In order to place the control of the swinging functions of the apparatus within reach of the operator, a switch 61 of the single pole, double throw type is located at the operatorsstation. The center tapof switch 61 is connected as shown in Fig. 5 by lead 68 with one terminal of generator 65. One of the selectable taps 61 is connected by lead 10 with one of the slip-rings which is in connection with winding 2|. The other selectable tap of the switch 61 is connected by the lead 1| with a slip-ring which is in connection with a winding 12 contained within the driving member 52 but shownv diagrammatically only in Fig. 5. The other terminal of the generator 69 is permanently connected, as shown, with the slip-rings which are in connection with the upper ends of the windingsv2| and 12. The operator may thus, by manipulation of the switch 61, energize either of the magnetic couplingv means I4 or I5 at will to produce either right-hand or ing of the cab vThe generator 69 is vpreferably ofthe type having a shunt field winding 13 having in series therewith a variable resistance 14 positioned at the operators location so that it may be regulated at will.

A generatorof this type has, as a typical characteristic, high open circuit voltage and a tendleft-hand swing-` ency for its voltage to drop as load is applied. A generator of this type is preferably availed of in the apparatus of this invention for the reason that the windings 2| and 12 are of high impedance and if normal operating voltage is applied thereto a considerable time elapses before full operating current becomes established. By use of the shunt type generator such as generator 69, however, application of high initial voltage of the generator to the windings 2| and 12 causes a rapid building up of current and a very prompt response on the part of the magnetic coupling means |4 and I6. By the time operating current is built up to normal operating levels the output voltage of generator 69 has fallen to normal operating levels and thus there is no condition under which excessive current is able to flow in any part of the circuit.

In order that the generator 69 exhibit thev characteristics desired, it is necessary that it be driven at a fairly constant rate and for this reason it is preferred thatgenerator 69 be mounted as shown in Fig. 2 and directly driven by the prime mover 4.

Because of the large moment of inertia of the cab and associated parts, including the boom 3, the swinging function is one accomplished largely under conditions of slip between the primel mover and the swinging cab. During substantially the entire swinging movement acceleration or deceleration is taking place. Therefore, in a machine in which a continuously running prime mover is employed, means which admit of slip must be employed. The magnetic coupling means of this invention admit of this slip without producing frictional wear and at the same time such slip is available for transmission of the torque required. The latter factor is of primary importance, since the torque transmittable by electromagnetic coupling means is greatest when the slip is greatest and falls oil= accordingly as slip is reduced. The electromagnetic coupling means of this invention are therefore capable of transmitting maximum torque at such times when maximum torque is desired, that is, when acceleration at the outset of the swing is required and when deceleration and reversal of direction of swing are required.

'I'he peak torque demand which the apparatus of this invention places upon the prime mover may be adjusted and fixed at any quantity desired by adjustment of the rheostat 14, or by initial selection of appropriate circuit constants. It is thus beyond the power of the operator, once the system is adjusted, to impose upon the prime mover more than a predetermined peak torque demand. This predetermined peak torque demand may be easily adjusted to a maximum at which the prime mover will continue to run at a reasonably constant rate of speed within the capacity of the governor to maintain satisfactory control. In this way the full power output of the engine is not impaired` and the apparatus as a whole is protected against disastrous acceleration. such as might cause crumpling of the boom. While initial high acceleration is thus precluded, sustained accelerations are nevertheless procured to an extent heretofore unattainable in drive systems employing friction clutches. Furthermore, arrangement of the generator which furnishes exciter current to be driven by, or in proportion to, the speed of the prime mover, causes a load-governing action to take place. The output voltage of the generator being thus driven will -fall oil. with any falling of! in speed of the engeraete and full power of the engine is made available `for the carrying on of simultaneous functions,

such as hoisting during swinging, and the like. The operator is relieved of the mental strain of Vattempting to avoid injurious and damaging shocks and is encouraged to press his operations toward maximum output. This makes possible a substantial overall increase in the work capacity of the crane so that a substantially smaller crane is capable of performing the work which has heretofore required acrane o substantially greater bulk, weight, and expense.

While this invention has been herein described in connection with a drive system adapted for producing the swinging movement of the crane, the other operating functions of the crane may be similarly driven and controlled, if desired. -Because 'of the high degree oi slip normally'existing in the swinging driving system, however,-

electro-magnetic coupling means are of p inrticun1 lar value.

While this invention has been herein vdescribed by reference to a, specic instance of deiinite application and use, it is intended that the protection of letters patentto be granted hereon be not unnecessarily limited thereby, but

that such protection extend to the full limit ci the inventive advance disclosed herein as defined by the claims hereto appended.

That which we claim as our invention is:

1. 'in a power transmission system. suitable for transmitting power from a running prime mover to a load to be accelerated and driven, the coml-e bination comprising a driving shaft adapted to be driven by said prime mover, a driven shaft adapted to drive said load-electromagnetic eddy current coupling means associated 'with said driving and driven shafts and adapted to trans'n mit torque therebetween when energized by an electric current, said coupling means including windings, a dynamo electric system of electric current supply having a drooping voltage chan acteristic mounted to be driven by said prime mover at a rate at all times substantially pro:J portional to the rate of said prime mover, and controllable means for connecting and disconn necting said winding to said dynamo electric system and adapted to apply the high opencircuit voltage of said-system to said winding when said connection is rst made and the lower volta age of said system after a substantial current iiow has been established.

2. En a power transmission system suitable for transmitting power from a running prime mover to a load to be accelerated and driven, the corn-s prime'mover for regulating the speed ci the same, a driving shaft adapted to be driven by said prime mover, a driven shaft adapted to 'drive said load, electromagnetic eddy current coupling means associated with said driving and driven shafts and adapted to transmit torque there@ bination comprising a governor mounted on said between when energized by an electric current. windings in saidcoupling means, a dynamo electric system of electric current supply having a drooping voltage characteristic mounted to be driven by said prime` mover at a rate at all times substantially proportional to the rate of said prime mover, and controllable means for connecting and disconnecting said winding to said dynamo electric system and adapted to apply the high open circuit voltage of said system to said windings when said connection is iirst made and the lower voltage of said system. after a substantial current Iiow has been established.

3. In an eddy current torque transmitter, the combination comprising a driving member, a driven member, means for establishing a magnetic field mutual to said members and extend= ing from one into the other through zones of localized high ux intensity, a primary air-gap between said driving and driven members subject to being increased by thermal expansion of one of said members, the flux path therethrough being impairable upon said increase, and a supplernentary air-gap between said members adapted to be diminished upon said thermal expansion and being positioned to provide a supplementary iiux path, the reluctance of which becomes diminished when said primary air-gap is increased by said expansion.

e. In an eddy current torque transmitter, the combination comprising a pole piece member, an eddy current member, said pole piece mein ber being provided with a peripheral groove, windings positioned in said/peripheral groove, a plurality of pole pieces ranged along the sides oi said peripheral groove and spaced from one another, the ends of said pole pieces being `positioned to lie within a surface of revolution coaxial with the axis of said pole piece member, said eddy current member being positioned in close proximity to the path swept by the ends o said pole pieces andbeing composed of4 electrically conductive magnetic material, and supplementary pole :lingers having faces positioned to lie in a surface of revolution normal to the surface swept by the ends ci said pole pieces, said supplementary iingers being secured'to said pole piece member. in close proximity to said eddy current member.

5. In an eddy current torque transmitter, the combination comprising an internat pole piece member, an external cylindrical sleevelllre eddy current member coaxial therewith, said pole piece member being provided with a peripheral groove, a winding positioned in said peripheral groove, a plurality of pole pieces ranged along the sides of said peripheral groove and spaced from one another, the ends ci said pole pieces being positioned to lie within a, cylindrical sur= face of revolution coaxial with the axis of said pole piece member, said eddy current member being positioned to surround said pole piece member in close proximity to the path swept by the ends of said pole pieces and being composed of electrically conductive magnetic material, and supplementary pole fingers having faces posi tioned to lie in a surface of revolution normal te the axis of said pole piece member, said sup0 plementary ngers being secured to said pole piece member. in close proximity to the end face oi said eddy current member.,

' -ENRY S. JACORS. "Y lli S. BURDICK. 

